The present invention relates generally to expiration flow rate measuring and monitoring devices, and more particularly to devices which are significantly simplified and improved over prior art units.
It has been found that the measure of peak expiratory flow rate is a good general indicator of the presence or absence of airways obstruction within the body. Thus such a device is useful in measuring the degree of response of the patient to bronchodilators. This is particularly helpful since obstruction of the airways usually associated with-lung disease, is measurable long before any other symptoms may appear. The measurement or the indication of a change in peak expiratory flow rate is an effective medical tool especially if screening techniques can be accomplished away from hospital or medical office environments, such as homes, places of business, etc.
Such a self administered test by the patient, who then could be in communication with his or her physician, could indicate the severity of an asthmatic attack, for example.
U.S. Pat. No. 4,158,360 is an excellent example of the prior art and the provision of such a device has in the past met the parameters required to accomplish the above ends. However, this device utilizes a central channel in an otherwise perpendicular upright member with a floating ball and a pin to position the ball at specific locations. The orifice opening may be restricted by a disc having varying diameter openings within its central face in order to vary the effect of the flow rate from the patient. This construction, while proving substantially acceptable, does not provide for simplicity of operation and preciseness in the measurement of the flow rate, since it requires the user to set or adjust the position of the ball prior to use.
U.S. Pat. No. 471,389 indicates an early construction of a spirometer utilizing a piston G biased by a spring K. It is obvious that the construction is more involved and does not allow for the accuracy present in the subject invention.
Another example of the prior art is British Patent No. 1,160,669 which discloses a spring loaded piston operating in the same direction as the flow of air from the patient. Once again, this construction is more involved than that of the subject invention, and does not provide the simplicity of construction and the accuracy of flow rate indication of the present invention.
Accordingly, among the principal objects of the present invention is to provide an improved spirometer.
Still yet a further object of the present invention is to provide a spirometer having spring biased piston mechanism to accurately indicate the peak flow rate of the patient as well as to assist in training to meet specific goals.
Still yet another object of the present invention is to provide a spirometer of the character described which will be simple and inexpensive to manufacture and yet will be durable to a high degree in use.